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  1. Maize Grain Yield Response to Preplant Nitrogen Placement At Different Distances from the Row J.L. Mullock1, J.T. Bushong1, B. Chim2, W.R. Raun1, and R.K. Taylor3 1Plant & Soil Sciences, Oklahoma State University, 2Crop & Soil Environmental Science, Virginia Tech, 3 Bio-Systems & Agriculture Engineering, Oklahoma State University INTRODUCTION RESULTS • Equipment with RTK Global Positioning Systems correction can provide sub-inch accuracy for nitrogen (N) applications • Maize grain yield has shown a positive response to mid-season N applied at distances closer to the row • This benefit was greater under hot, dry conditions. OBJECTIVE Figure 4. Mean maize grain yield response to preplant N placement at different distances from the maize row, Lake Carl Blackwell, OK, 2012. • This study was conducted to evaluate the effect of preplant N placement at different distances from maize rows on grain yield • Preplant N Placement, from Row • LAKE CARL BLACKWELL • No significant main effect for preplantplacement, from row • Trend analyses not significant • HENNESSEY • Significant linear trend yield to increase with increased placement of N from the row (α=0.05) • Quadratic trend, not significant • Cubic trend for placement (α=0.10) Figure 2. Mean maize grain yield response to preplant N rate, Lake Carl Blackwell, OK, 2012. • Preplant N Rate • LAKE CARL BLACKWELL • Over-all average yield of 3168 kg ha-1 • No significant main effect of N-rate (α=0.10) • Quadratic trend for N-rate (α=0.10) • No linear or cubic trend for N-rate • HENNESSEY • Over-all location yield average of 1981 kg ha-1 • No significant main effect of N rate • No linear, quadratic, or cubic trend for N-rate Lcb Figure 1. Preplant N applicator with moveable toolbar to change distance from the planted row mounted on an RTK equipped tractor. MATERIALS & METHODS • Study was conducted at two drylandlocations, summer of 2012 • Lake Carl Blackwell (LCB) - (Pulaski coarse-loamy, mixed, superactive, nonacid, thermic UdicUstifluvents) • Hennessey - (Bethany fine, mixed, superactive, thermic PachicPaleustolls) • Preplant N rates, 0, 56, 112, & 224 kg N ha-1 • Nitrogen was applied in the form of urea-ammonium nitrate (28-0-0) • Preplant N distances from the maize row were 0, 8, 15, 25, and 38 cm. • Treatments were arranged in a RCBD with 3 replications. Figure 5. Mean maize grain yield response to preplant N placement at different distances from the maize row, Hennessey, OK, 2012. CONCLUSIONS • Yield levels were low at both locations, and response to N placement was reduced • After 2 site-years, results are inconclusive and evaluation will be continued Figure 3. Mean maize grain yield response to preplant N rate, Hennessey, OK, 2012. OKLAHOMA STATE UNIVERSITY